1. Field of Invention
The invention relates to a pump for dispensing a substance, in particular a cosmetic.
2. Description of the Related Art
French patent 2 728 809 discloses a pump comprising a pushbutton mounted to move relative to a support which is secured to a receptacle containing the substance to be dispensed, the pushbutton having a circularly cylindrical central duct provided with radial openings at its bottom end, the support defining an annular pump chamber of variable volume around said duct.
A diaphragm made of elastomer is mounted on the support.
The diaphragm has a circularly cylindrical central portion in the form of a sleeve that is open at its top end and closed at its bottom end.
The central duct of the pushbutton is inserted into the diaphragm until it bears against the bottom of the sleeve-shaped central portion.
The diaphragm constitutes a resilient return member enabling the pushbutton to be returned to its initial position after a quantity of substance has been dispensed.
In addition, during the return movement of the pushbutton, the diaphragm presses against the central duct, thereby isolating the pump chamber and making it possible to prevent air from penetrating into it.
The diaphragm thus acts as a delivery valve. The diaphragm also acts as a suction valve.
Such a pump has the advantage of comprising only a small number of parts and thus of being relatively inexpensive to manufacture.
Nevertheless, that pump does not give full satisfaction, the Applicant company having observed that the pushbutton tends to jam and/or to dispense poorly and in non-uniform quantities.
The present invention seeks to improve the operating reliability of a pump of the type defined above, i.e. comprising a support-forming assembly for securing to a receptacle containing a substance to be dispensed, a moving member co-operating with the support-forming assembly to define a pump chamber of variable volume, and an elastically deformable diaphragm secured to one of the support-forming assembly and the moving member, the diaphragm being arranged so as to deform elastically when the moving member is displaced relative to the support, the pump further comprising a suction valve-forming element arranged to oppose any return of substance towards the receptacle while the volume of the pump chamber is decreasing, and a delivery valve-forming element arranged to oppose any entry of air into the receptacle while the volume of the pump chamber is increasing.
In the pump of the invention, the delivery valve-forming element is made by means of a shutter-forming element that is separate from the diaphragm and the diaphragm is prestressed when the pump is at rest.
Thus, in the invention, the diaphragm can act as a spring without any fear of the moving member jamming; since the element forming the delivery valve is distinct from the diaphragm, there is no risk of the diaphragm impeding departure of the substance leaving the pump chamber.
Since the diaphragm is prestressed when the pump is at rest, any clearance at rest is avoided and any risk of substance leaking in the event of the pump being transported is reduced.
In the known pump described in French patent 2 729 809, the diaphragm is tensioned when the pushbutton is pushed in, and one consequence of this tension can be to impede the flow of the substance leaving the pump chamber and to make priming difficult.
In a particular embodiment, the diaphragm has a central portion in the form of a sleeve that is open at one end and closed at its opposite end, the moving member bearing against said central portion.
Still in a particular embodiment, the moving member, i.e. the pushbutton, for example, comprises first and second moving portions that are movable relative to each other, the first portion co-operating with the support-forming assembly to define the variable-volume pump chamber, the second portion being movable relative to the first portion between firstly a dispensing position in which it is suitable for entraining the first portion in the direction to decrease the volume of the pump chamber, and secondly in a position relating to suction in which it is suitable for entraining the first portion in the direction to increase the volume of the pump chamber, the shutter-forming element being secured to the second portion, the first portion having a passage to enable substance to flow towards a dispensing endpiece, the shutter-forming element being movable relative to the first portion between a position relating to closure in which it closes said passage, and a position relating to dispensing in which it ceases to close said passage.
Such a pump is relatively easy to manufacture since it has only a small number of parts that are easy to assemble together.
In a particular embodiment, the shutter-forming element is in its position relating to closure while the second portion of the moving member is in its position relating to suction, and the shutter-forming element is in its position relating to dispensing while the second portion of the moving member is in its position relating to dispensing.
Preferably, the shutter-forming element bears against the diaphragm.
When it has a central portion in the form of a sleeve, the shutter-forming element advantageously bears against the bottom of said central portion.
Still in the context of the diaphragm including a sleeve-shaped central portion, the above-mentioned passage is advantageously defined by a chimney engaged inside said central portion.
In which case, the shutter-forming element advantageously has a rod fixed at one end to the second portion of the moving member, said rod extending inside the chimney and being provided at its opposite end with a valve-forming portion suitable for bearing in leakproof manner against the chimney so as to close it.
In a particular embodiment, at least one of the first and second portions of the moving member includes a sealing lip suitable for bearing in leakproof manner against the other portion during relative displacement of these two portions.
Thus, the relative movement of the two portions of the moving member can take place without any fear of the substance leaking.
Preferably, the sealing lip is formed on the first portion at one end of the above-mentioned passage.
In a particular embodiment, the first portion is snap-fastened in the support-forming assembly.
Advantageously, this first portion corresponds to the bottom portion of a pushbutton comprising two telescopic portions.
In a particular embodiment, the support-forming assembly includes an insert on which the diaphragm is mounted.
Still in a particular embodiment, the diaphragm has a peripheral portion defining a groove enabling it to be mounted on the insert.
In a particular embodiment, the insert has a suction valve integrally formed by molding a plastic material.
In a variant, the peripheral portion of the diaphragm includes a flexible lip forming a suction valve, the support-forming assembly having one or more openings enabling substance to reach the pump chamber while its volume is increasing, said opening(s) being closed by the flexible lip while the volume of the pump chamber is decreasing.
The invention also provides a receptacle fitted with a pump as defined above.